The purpose of the research described is to add to existing knowledge of the functional significance of cerebral structures involved in higher-order perceptual processes. Patients with verified, unilateral brain damage will be studied in experiments that assess function in both the visual and the tactual/kinaesthetic modalities. In all experiments, the locus of brain damage represents an independent variable in the belief that causal relationships between structure and function will emerge with this approach. The questions posed are the result of integrating findings from studies of normal human perception, and knowledge of brain/behavior relationships that have been established in studies on nonhuman primates. A quantitative theory of perception, adaptation-level theory, provides one conceptual framework for challenging the perceptual systems appropriately, while knowledge of the anatomical and physiological substrates underlying perceptual processes in the monkey provides the basis for interpreting behavioral deficits in biologically meaningful terms. Test procedures derived from animal experimentation, when adapted for humans, allow for the assessment of perceptual capacity that is language-free, and avoid the problems of response bias inherent in many experimental paradigms. The major areas of interest in the investigation of internal representations of experience are (1) context-sensitive perceptual mechanisms, (2) unimodal and intermodal spatial representations, (3) registration of compound stimuli, and (4) affective-perceptual integration. An important feature of the proposed studies is the methodological advantage accruing from use of tests that are short, yet provide quantitative results and are informative about sensory deficit as well as higher-order processes. Additionally, while the goal of the research is to understand brain mechanisms as they relate to normal and impaired perceptual functioning, all of the tests lend themselves to clinical application.